1. Field of the Invention
The present invention relates generally to barrier and intrusion detection systems, and more particularly, to an alarm locator module for use with a picket barrier fence.
2. Discussion of the Prior Art
Existing technology in perimeter security systems typically includes the use of various types of fences in combination with barbed obstacles and various types of alarm systems. Such alarm systems have typically utilized some type of electronic sensor to augment the fence barrier and create an alarm if the perimeter is breached. In general, the more sophisticated perimeter systems currently in use combine an aggregate of the above devices, for example, e.g., fences, barbed obstacles and electronic sensors, in order to provide first, a notice of the attempted intrusion, and then a delay of the actual intrusion. Little technology exists which teaches combining such devices in what is considered to be an optimal manner, and few alarm systems are capable of determining exactly where the intrusion has occurred. The result achieved by prior art detection systems has been that the physical barrier is often diminished by the effectiveness of the sensors, while the sensors are often affected by the physical barrier. In addition, once the perimeter has been breached, most systems provide little or no support in the process of apprehending the intruder.
Prior art attempts to solve the problem are disclosed in U.S. Pat. Nos. 4,097,025 to Dettmann, et al; 4,155,083 to Slaats, et al; and 4,197,529 to Ramstedt, et al. Dettmann disclose vibration sensors connected to a fence which detects vibrations of the fence occurring during an intrusion attempt and generates signals for input to the alarm system. Slaats disclose a fence made of wire elements comprised of coaxially conductive layers separated by a thin insulated layer. Intruder pressure applied to the fence generates a contact resistance between the conductive layers or a change in the capacitance between the layers that results in a measureable event, which upon detection, causes an alarm system to be actuated.
A timed domain reflectometer is utilized by Ramstedt et al. in combination with an external conductive sheath and an internal conductor separated by a layer of insulating material, such that any deformation of the sheath relative to the central conductor generates a variation in the impedance of the cable which can then be detected and used to actuate an alarm.
Each of the above prior art approaches are subject to the disadvantages of: requiring an aesthetically unpleasing fence structure; providing an apparatus which can be easily violated by a knowledgeable intruder; having a high susceptibility to false alarms caused by non-intruders; and often being ineffective in determining the point of intrusion.